This invention relates to the field of fiber optic splice closures, and more particularly, this invention relates to the field of fiber optic splice closures and the routing of optical fiber ribbons therein.
Fiber optic cables often contain multiple optical fiber ribbons arranged in a stacked, sequential formation. These fiber optic cables containing the optical fiber ribbons connect into a fiber optic splice closure such as disclosed in U.S. Pat. No. 5,323,480, assigned to Raychem Corporation, the disclosure which is hereby incorporated by reference in its entirety.
The fiber optic splice closure in the ""480 patent includes a housing having a cable termination that secures one or more fiber optic cables into the housing. A plurality of splice trays are positioned within the housing and each have an end pivotally connected to a bracket and moveable between a stacked position and raised position to facilitate access to an underlying splice tray. Transport tubes protect the optical fibers and optical fiber ribbons, despite any bending of the fibers and ribbons. As disclosed, optical fiber ribbons, such as LightPack(copyright) fiber optic cables, are offered by ATandT and other companies and can be readily bent only in a direction normal to their major dimension, which is equivalent to a minimum bend radius of individual fibers. The ""480 patent discloses these generally flexible transport tubes, which carry optical fibers from one or more fiber optic cables to respective splice trays. Each transport tube has a longitudinal axis and a mechanism for imparting to the transport tube a differential flexibility between first and second directions transverse to the longitudinal axis.
Although the ""480 patent discloses a mechanism for imparting differential flexibility, this splice closure does not provide a solution for arranging optical fiber ribbons after they are cleaned, routed and spliced. During any cleaning and routing stages, the original stacked formation of any optical fiber ribbons is lost. Identification of each ribbon must be re-established, usually at the ends, before splicing can be completed. In an attempt to solve this problem, some workers label each ribbon along its length. This labeling, however, is often hard to see and sometimes comes off during cleaning. After the optical fiber ribbons are spliced, there is also no guaranty that the ribbons can be removed back to the central core tube (CCT) or a loose buffer tube (LBT), without the optical fiber ribbons being entangled with the other ribbons.
Another disadvantage of a round feed tube, such as the disclosed transport tubes, is the poor alignment of optical fiber ribbons. Also, the ribbons rotate within the round tube and are allowed to bend in any plane. When adjusting individual ribbons longitudinally within a round tube that has been routed (containing bends), pressure could be exerted to the innermost ribbons, specifically the first and last (usually the number 12 ribbon) of the innermost optical fiber ribbon. This high stress area exists because of the contour difference between the external ribbon stack (of rectangular profile) and the internal wall of a round tube. Additionally, a high coefficient of friction exists when adjusting one of a group of ribbons longitudinally in the typical round tube. The ribbon group is typically either not in a stacked formation or a helix exists along the routed length making individual ribbon movement restrictive.
The present invention is advantageous and uses a ribbon organizer that has an interior dimension that substantially matches the size and shape of a plurality (or stack) of optical fiber ribbons. In operation, a plurality of optical fiber ribbons are stacked together in a group and exposed for a splicing operation. The ribbon organizer of the present invention is installed over the optical fiber ribbons at an opening of the fiber optic feed tube. The interior dimensions of the ribbon organizer substantially match the size and shape of the plurality of optical fiber ribbons. The original stacked, sequential arrangement of the optical fiber ribbons is re-established by sliding the ribbon organizer down along the length of the optical fiber ribbons, thereby orienting the optical fiber ribbons into their original positions as they are within the fiber optic feed tube.
The ribbon organizer is preferably rectangular configured, and in one step, can comprise the step of longitudinally splitting a ribbon organizer that is slid along its length, and then wrapping the split ribbon organizer around the optical fiber ribbons. In yet another aspect, the method can comprise the step of installing the rectangular configured ribbon organizer by sliding the ribbon organizer over the fiber optic feed tube at a location where the optical fiber ribbons extend out of the fiber optic feed tube. In yet another aspect of the present invention, grease can be blocked from migrating out of the fiber optic feed tube by sliding the ribbon organizer into the fiber optic feed tube.
A plurality of ribbon organizers can also be grouped along a plurality of optical fiber ribbons for controlling the storing and routing of fibers within the fiber optic splice closure. The fiber optic feed tube can comprise one of either a central core tube or loose buffer tube. The ribbon organizer can be formed from substantially flexible material to allow bending of the optical fiber ribbons without twisting and bending of the optical fiber ribbons. The ribbon organizer can also include dual channels for allowing two sets of a plurality of optical fiber ribbons to be organized. The ribbon organizer is substantially rectangular configured in one aspect of the present invention.
In yet another aspect of the present invention, a fiber optic splice closure includes a housing and a fiber optic feed tube secured to the housing. The fiber optic feed tube has a plurality of fiber optic ribbons. A plurality of splice trays are pivotally mounted within the housing for receiving spliced fiber optic ribbons. The splice trays are moveable between a stacked position and a raised position that facilitates access to an underlying splice tray. A ribbon organizer is positioned over the optical fiber ribbons and has interior dimensions that substantially match the size and shape of the optical fiber ribbons. These are positioned so as to re-establish an original stacked, sequential arrangement of the optical fiber ribbons into their original positions as they are within the fiber optic feed tube.
In yet another aspect of the present invention, the ribbon organizer is substantially rectangular configured and includes dual channels for allowing two sets of a plurality of optical fiber ribbons to be organized. The ribbon organizer can also be inserted within a fiber optic feed tube to aid in blocking grease from migrating out of the fiber optic feed tube.
In still another aspect of the present invention, the ribbon organizer can contain a tracer mark to identify a side containing a first optical fiber ribbon. This ribbon group will not rotate inside the ribbon organizer even during twisting and bending of the organizer. The ribbon organizer can typically include a two orifice or single orifice rectangular shaped organizer.